Control system for electric motors



g- 1930- Y J; F; SCHNABEL 1,773,409

CONTROL SYSTEM FOR ELECTRIC MOTORS Filed March 1926 5 Sheets-Sheet l' INVEN TOR.

g- 19, 1930- J. F. SCHNABEL 1,773,409

CONTROL SYSTEM FOR ELECTRIC MOTORS Filed March 1926 '5 Sheets-Sheet 2 INVENTOR. v J20: v7 Jt/flidd & 6%?! A TTORNEYQ Aug. 19, 1930. SCHNABEL 1,773,409

CONTROL SYSTEM FOR ELECTRIC vMOTORS Filed March 3, 1926 3 Sheets-Sheet I5 1 48 7* LYVENTOR.

BY I v ATTORN- Y5 Patented Aug. 19, 1930 UNITED STATES PATENT OFFICE JAMES F. SGHNABEL, OF CLEVELAND, OHIO, ASSIGNOR TO THE CLARK CONTROLLER COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO CONTROL SYSTEM FOR ELECTRIC MOTORS Application filed March 3, 1926. Serial No. 91,929.

The present invention relates to systems tor the control of hoists of cranes or other hoisting mechanism and particularly provides for controlling mechanism for providing smooth and accurate control of the hoisting motor during both the hoisting and the lowering periods and under the widely varying load conditions usually met with on cranes.

The present controller also provides a safe ly dynamic circuit at the off position of the controller which circuit will prevent the load from descending rapidly in case of failure of the holding brake.

Another object is the provision in the controller of means for governing the speed of the motor during lowering so that the operator can accurately lower short distances slowly or can lower through longer distances at as hi gh a speed as is permitted by the general design of the hoist and at the same time, the operator is enabled to control the lowering of an empty hook where power must be applied to the motor from the source of supply.

In particular the present controller is degncd to accomplish the above results with fewer part-s than previous types of controllers and to improve the operation especially in lowering by making it possible to obtain much slower speeds on the first few contact points when lowering heavy loads and at the same time providing higher speeds when lowering the empty hook on the last points of the controller and also to provide means for adjust ing the controller to meet the requirements of individual motors, brakes and particular operating conditions. To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawings and the following descriptionset forth in detail certain mechanism enrbmlying the invention, such disclosed means cons ituting, however, but one of Va.-

' r1 mechanical forms in which the principle oi the invention may be used.

In said annexed. drawings Fig. 1 is a diagrammatic layout of the controller contacts and showing the resistors and the connections between resistors and the contacts; Fig. 2 is a diagrammatic view of the controller arm, sho ing the. cross contacts employed and diagrammatiCally showing the oil? position of said controller; Fig. 3 is a wiring diagram showing the controller in its hoisting position and showing in full lines the controller as arranged on the first contact points and in dotted lines the position on the last contact points; Fig. 4 a wiring diagram showing the safety braking circuit at the olt position of the controller; Fig. 5 is a. wiring diagram showing the dynamic braking circuit of the controller in the lowering position, the full lines indicating the first contact points and the dotted lines indicating the circuit at the last contact points during lowering; Fig. 6 is also a wiring diagram of the motor circuit in the lowering position to more clearly show the arrangement when the motor is driving down a light load; Fig. 7 is a View similar to Fig. 1 but showing modified arrangements of resistance banks and groups of contacts; Fig. 8 is a wiring diagram similar to Fig. 3 but showing the use of tour banks of resistance,- Fig. 8A is a view similar to Fig. 8 but showing a slightly modified wiring arrangement; and Fig. 9 is a wiring diagram similar to Fig. 5 but showing the tour banks of re sistances as in Fig. 8.

On the drawings, are conventionally shown a. motor armature 1, a series field winding 2, a magnetic brake 3, the banks of resistors 4A, 5 and 6, and the controller arm 10 for varying the resistance and for controlling the various circuits which are to be obtained during the hoisting, holding and lowering of leads by the motor. In Figs. 1 to 6 are shown three banks of resistors, with four groups of con t\.CtS l-fl-., 14A, 15 and 16, the groups of contacts 14 and 14A both being connected to the resistance l-A, the group of contacts 15 to the resistance 5, and the group of contacts 16 to the resistance 6.

The controller arm 10 best shown in Fig. 2 and consists of a hub 11 carrying two arms at substantially right angles to each other, these arms carrying contact fingers or brushes p5 of contacts or and with it u N cud the dead plate between groups. One of the 2 rms M is provided with two pairs oi electrically connccteu fingers or l rushes Ll ulti 1: 3i and 25 and 251i. while the other arm in single finger or brush 26 and ii" 7 these two huge being electrical connected by a suitable connector lair or the like and roller arm 10 is shown as provided the cont with a ct nventional operat handle 18.

nei'erriig to the draw it will be seen ha in the hoisting p: n, the resi. ant-c ace which is iti've (-t) l, the re- 1 shunt cira he circuit in its position, and on the first contact 19 illustrated in -lull lines the main sthrough {1GP terminal, he positi -e lin 0, pov lat cont: ct hrishcs arm to the lligthrough Vila-LA to the armature terminal 3i, t i Lure l the series held 2, the magnetic lllillic to the rake terminal l5, and 1e entire resistance l brushes 2:) and Q54 unit 5 and the fingers or to the negative center plate 13, blowout coil 17 and the negative line 31 to the ne 'ativc terminal. its the motor lioi it the cm trolici' handle i moved counter-clockwise, the contactlinger 2-iiasses over the group 1 of contact rain 1 thus cut 'ng out successive resistors in t ii; i -A in the circuit, while the contac r 95 sii'niiarly cup I 26 and cf reac nected contact points El and 56 at the ends of the banks ll and 16 respectively.

In order to more closely control the resistance in the shunt circuit the inter-conncctions T4- inay he of graduziitcd resistance Yalues or may have graduated resistances Slii'iserted, such re stances and graduated values being illustrated at: fi l in Figs. 2-3, 5 and G. The use of such added resistance in the interconnections Tl will depend upon the value of the resistance 3 or upon the ance of the separate resistor steps, and the hoisting and lowering characteristics of the entire hoisting mechanism to which the controller is applied.

The interconnectin: between the contacts of groups lland lift may he \':1ii61'l as hetween the several contacts of each group to obtain the required filllOLilltS of resi ance in the circuit at tl e rarious contact points the controller handle moved.

lVhen the controller is at the oil position. a safety braking" circuit is obtained as hot slit wn in Fig. l in w ich position a shunt circuit i8 with no res'v "iosed anout the motor armature and I t. thus making the a generator ii ri'itatcd in the lO'fiOllDQ i ii ion. This circu't ai u-d through c plates 60 and ($1 on coitrollcr and brushes 96 and 27 on the ller arn'i the contact (if) ha 7 :1 connect line 5.1. with i' and. the pin 61 a connectial A of the arm:

th the terniii i 1 ng the internal circuitinclud ingthe a mature and iield but not including in: gnetic brake.

In Fig. 5 the lowering circuit shown a; considered with overhauling load, the two contact brushes 26 and Q? oi? the arm +15 having been moved to the end contacts of group lei-A and 15. Jitter the lrushes 26 and 27 have passed over certain contacts of groups .l-A and 15, the fingers and 25A hax'i assed over the unconnected contacts conncct the resistance 6 in series with the posh tilt (3 terminal through center plate and line 30, thus providing a starting c rent suiiicient to release the n'iagnetic hralte and to startv the lowering action as the linger-:1

and 24:91 hating pav scd over the unconnected contacts, complete the parallel circuits through contact cup 14, plate 13, )lUW out coil 17, the negati to line 31, to the negative terminal. Thus in lowering, the circuit is changed to nialte a shunt motor or generator and as the controller moved, the closed motor circuit, or dynamic braking circuit under an o.'ei.'liauiing load, has the resistance 5 gradually added and the bank 4A is likewise gradually added into this closed motor circuit by the movement of arm l5 and lingers 2G and 27. Thus resistance is in creased rapidly in the closed inotor circuit to obtain proper speed control of the overhauling load at all times.

(iii

In Fig. 6, the same motor circuit is illustrated as in Fig. 5 but arranged slightly differently to better illustrate the arrangement during lowering when the motor is used to drive down an empty hook or a load that is not heavy enough to overhaul. As in Fig. 5, the first power position shows the resistance 6 connected to the positive terminal through line 30, positive plate 12 and fingers and 25A, while the fingers 26 and 27 close the motor circuit through certain contact points of resistance group contacts 14A and 15 thus starting the motor as contacts 24 and 24A close the circuit to the negative terminal through the other end contact of bank 4A, the negative plate 13, blow out coil 17 and line 31. Thus at the starting 1;:osition, the circuit provides a shunt motor with resistance 6 in series with the line and part of resistance 4A also in series with the line but with a closed circuit around the armature 1, field 2, and brake 3 so that the motor can act as a dynamic brake if the load starts to overhaul. To maintain the armature circuit and the field circuit in the desired resistance ratios, it will be noticed that as the resistance 5 is added into the parallel field circuit, the resistance 6 is being removed from the line circuit and also some of the resi stance 4A while a portion of the resistance 4A is also added to the armature circuit. As the fingers 27 and 24 relatively pass each other on the resistance bank 4A, the circuit rapidly changes its characteristics, the resistance in the armature circuit from the positive line through the armature to the negative line being rapidly reduced as both resistance 6 and resistance 4A are out out of the circuit while the resistance in the field circuit is increased as resistance 5 and resistance 4A are being added although resistance (5 is being removed. Thus at the full lowering position of the controller, the armature is substantially across the line, while the field has resistances 4A and 5 both in series with it across the line. In this manner the field which is of low resistance due to its normal use as a series field is always provided with suificient additional resistance to be used satisfactorily as a shunt field during the lowering operation.

In Figs. 7 and 8, a modified wiring diagram is shown, similar to Figs. 1 and 3, but showing a fourth bank of resistors 4 instead of using the two groups of contacts 14 and 14A connected to the same resistance bank 4A. Thus the controller arm contact finger 26 contacts group 14 and cuts bank 4 into the variable shunt circuit while the controller finger 24 operating over group 14A cuts the bank 4A into the motor circuit. Instead of using the one bank 4A for both the motor circuit and the shunt circuit and controlling this bank in the two circuits from both contact groups 14 and 14A, the shunt circuit is separately controlled from the bank 4 by the contact 26 on the controller arm and the bank 4A in the motor circuit by the contact 24 on the controller arm. The same type control is obtained for the lowering circuit, the contact finger 27 passing over the group 14A and thus controlling the bank 4A while the bank 4 is controlled by finger 24 passing over group 14. Three banks of resistors with the double control for one bank is found satisfactory for some types of installations but the four banks are preferred for many types on account of the adjustable features secured in this arrangement.

Furthermore the four bank type of controller with an adjustable tap provides better operation for both the hoisting and lowering circuits and allows the proper amount of resistance to be maintained in the motor armature circuit during the entire controller range for lowering. This forces sufficient current through the field circuit to release even a very sluggish acting magnetic brake. By the use of the adjustable tap connection 7 5 between the end contact of one bank 4 and the other bank 4A, there is always left a predetern'iined fixed amount of resistance in the armature circuit and this amount can readily be adjusted to meet the actual conditions of the hoisting mechanism and motor. The adj us-table'tap 75 also makes it possible to change and control the field strength and thus adjust and vary the final speed of both hoisting and lowering to meet the actual operating conditions but at the same time does not change the use of the entire banks of resistors 4A and 5 in the internal or dynamic braking circuit. This adjustable tap arrangement is best shown in Figs. 8 and 9, the bank 4 of resistance which is in the variable shunt circuit being connected not directly to the armature line but to one of the taps of the resistance bank 4A and this connection 75 being adjusted to fit the particular motor and field operating con-- ditions. The same adjustment is shown in Fig. 9 for the lowering circuit.

In Fig. 8A is shown a modified way of accomplishing the same result. In this case while only three banks of resistances are employed as in the first form, the fourth group of contacts is not interconnected but are connected together by short leads 39, also shown in dotted lines on Fig. 7, thus substantially short circuiting all of these contacts. \Vhere such constructions is employed the resistance of the banks is preferably of suificient value to equal the combined resistances of banks 4 and 6 both in the armature shunt circuit and the lowering circuit, the adjustable tap 75 allowing the same fine adjustment for speed and motor control as before as the bank 4A is used in the same manner as in Figs. 8 and 9.

Briefly the operations of the device is as follo e: To hoist a load, the controller arm is moved from the otl position as indicated in Fig. in a counten"lockivise direction thus closing the armature shunt circuit by the connected con acts and 27 on arm J through contact s l-l and 1b and the motor circuit thro grh the pairs of contacts E l-ll and 2?. through contact groi ps 1i: and 15 and center contact plates and ill. As the i cuit resistance in arm is moved the shunt c r creases by adding resistor of bank 6 and finally by rapidly adding haul: l in Figs. 1 and 3 or by gr; anally adding both banks as in the form shown in Figs. 7 and 8 and this circuit breaks or is opened when the fingers 26 and 2'? reach the dead contacts 54 and 56 which takes place before the motor circuit fingers Ql and Q5 reach the end con tacts of banks 1 1A and 15. In the oil position of the controller, the arm c=tz-nt ts t 24d. 25 and 25A rest on tl c i and 34: ant. the only closed circui' is l h dynamic braking circuit ClOSQ(. by I re connected lingers 26 and 27, the and (il around the irough the magnetic brake 3. In the lo tlon, the controller arm movand thus the braking" circuit the end contacts of banks 14A and 1 the contact brushes 2G and 27. thus the magnetic bra e rent flow will release the same. The bank 6 of resistance is adc ed into the circuit between the positive terminal and the motor and the bank l is connected between the motor circuit and the negative terminal.

whether are obtained :rors and four These same circ three banks of res contacts are employed or tour ban o resistors and four groups of contacts a e employed. as will be clear from Figs. inclusive.

In the present: controller, rour roups or contacts are employed and are controlled by i tour contact brushes on the ore; i i

arm. and thus three or tour banks o'l. resistors may be employed at all tim from the or face plate and set of arms. nu, only does the use of the crossed con roller arm all three or tour b: n rs of r the present form tr be c permits these banks to h desirable manner. In hoi desirable to have the individu resistors of l h ghest different resistance values with toe V resistance at the first contact and the values gradually reducing to the last contact point. In lo'vvering particularly v'ia r tors shov; unloved but it. also used in the most he load it is 'n the d braking circuit, it is desirable to intro the resistances into the circuitin the opposite Way, the steps of lovv resistance value b first introduced and the steps of high re. ance value beingintroduced last. Thus in the present controller, the same pair of banks of resistors and groups of contact points are employed to introduce resistance into the circuit for both hoisting and lowering but in one case the arms and lingers move over the contacts in one direction and in the other case in the opposite direction. The same desirable arrangement is obtained from the third bank which is used the resistance in the variable resistance armature shunt circuit in hoisting in which use it is desirz ble to add resistances of constantly increasing value. This bank is also used in lowering as the resistance in the line between the positive line and the parl el circuits and is gradially reduced, the first steps being; those of highest resistance and gradually decreasing in resistance value.

-'*ill these tuiturcs are obtained from the sii ace plate and one ol crossed arms aim the same sets of contacts are in constant use at all The W0 sets of contacts for one bani; may be in use at the same time and this double us of one bank makes it possible to oblai he desired type of resistance k. vantage both to the manutzu-turer and to the because the contacts and dead plates on the taco ot the controller the details of the oyv out coil, contact brushes and. holders all substantially the same as those on confor other motions which would be on the same c ane, such as the controllers or the bidge and trolley and sometimes other auxiliary motions. Heretotore, it has ordinarily been necessary to have special types of contact plates and rings on the corn trollcr tor the ho stingoperation which includes a dynamic braking: circuit but due to the cro *ntact' arms used in the present controller. has been found possible to adapt the standard type of reversingcontroller plates to the present type of controller and thus manutacturing costs are reduced and operating costs are likewise reduced as only one of are parts are necess ry for several controllers.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed. provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out and distinctly claim as my invention 1. In a motor control system for hoists and the like, the combination of a motor, having an armature, a field and a magnetic brake, and a. controller adapted, during lowering, to connect said armature and a variable resistance in a power circuit and to connect the field and brake with a second variable resistance in a. parallel power circuit, said con troller being also adapted to sin'uiltaneously close a dynamic braking circuit around said armature, said field and said brake through said two resistances, and said controller being adapted to open the power circuit while a portion of said two resistances are main tained in said braking circuit and then gradu ally removin said two resistances from said braking circuit.

2. I11 a motor control system for hoists and the like, the combination of a motor, having an armature, a field and a magnetic brake, and a controller adapted, during lowering, to connect said armature and a variable resistance in a power circuit and to connect the field and brake with a second variable resistance in a parallel power circuit, said controller being also adapted to simultaneously close a dynamic braking circuit around said armature, said field and said brake through said two resistances, said controller being adapted to open the power circuit while a portion of said two resistances are maintained in said braking circuit, and being finally adapted to maintain said dynamic braking circuit around said arm and field with no resistance therein.

3. In a control for hoisting motors, the combination of the motor armature and field connected in parallel circuits for lowering, and providing a dynamic braking circuit, a bank of resistance having one end connected in series with the armature circuit, an adjust able tap connection between one line terminal and a point on said bank of resistance to leave a predetermined amount of said bank in circuit with said armature at full on lowering position and means for adjustably connecting said field circuit to said bank during lowering to obtain varying lowering speeds.

4. In a control system for hoisting motors, the combination of a motor armature and a field and magnetic brake connected for lowering in parallel circuits, and a controller providing a bank of resistance having one end connected to the armature circuit, a second bank of resistance having one end connected to the field and brake circuit, means for adjustably connecting varying amounts of said two banks in a. dynamic braking circuit, and an adjustable tap connection between said first bank and one of the line terminals, to obtain an adjustable predetermined amount of resistance in the field circuit at the full on lowering position.

5. In a control system for hoisting motors, the combination of a motor armature and a and adapted for varying connection by said controller arm with the other line terminal, two of the controller arm brushes for two groups being adapted to close a dynamic braking circuit through said first and second banks, said adjustable tap connection being adapted to provide an adjustable predetermined resistance in the field circuit and a different amount of resistance in the armature circuit at full on lowering position to obtain the desired full on lowering speed.

Signed by me this 1st day of March, 1926.

JAMES F. SCHNABEL. 

